- #1

- 3

- 1

- TL;DR Summary
- how to calculate it?

I am 3d printing micro wind turbine blades (5-10 watts output in 30mph wind), but anyway I am using naca foil shape twisted to make it.

This is not technically a propeller (cannot be efficiently used to push air) because it is generating power from moving air: it is a repeller, but regardless the theory is the same for either, and I need to understand this for making propellers as well.

My question is, how much twist should it have, and how would I calculate the twist correctly?

I have now a linear twist, so starting at 40 degrees at the hub, out to 85 degrees at the tip and it spins really fast in the wind, but it can't be optimal.

When I really think about it, it seems that the twist along the length is non-linear. Meaning it should twist more and more closer to the hub with less rate of change of twist toward the tip. Is this correct? Is it 1/x ? If so, what is the starting twist angle supposed to be?

Further, should the camber or foil shape itself also vary along the length? It seems it should, but how do I calculate this?

This is not technically a propeller (cannot be efficiently used to push air) because it is generating power from moving air: it is a repeller, but regardless the theory is the same for either, and I need to understand this for making propellers as well.

My question is, how much twist should it have, and how would I calculate the twist correctly?

I have now a linear twist, so starting at 40 degrees at the hub, out to 85 degrees at the tip and it spins really fast in the wind, but it can't be optimal.

When I really think about it, it seems that the twist along the length is non-linear. Meaning it should twist more and more closer to the hub with less rate of change of twist toward the tip. Is this correct? Is it 1/x ? If so, what is the starting twist angle supposed to be?

Further, should the camber or foil shape itself also vary along the length? It seems it should, but how do I calculate this?